1. Field of the Invention
The present invention relates to a laminated electronic part. More particularly, the invention relates to a laminated electronic part such as a laminated piezoelectric actuator used for a precision positioning device in an optical device, used as a drive device for preventing vibration or used as a drive device for injecting fuel in an automotive engine.
2. Description of the Related Art
A laminated piezoelectric actuator which is a kind of the laminated electronic part utilizes an inverse piezoelectric effect in that a piezoelectric plate expands and contracts when a voltage is applied thereto. In this case, the amount of expansion and contraction of a piece of piezoelectric plate is very small. Therefore, a laminated piezoelectric actuator has heretofore been used laminating a plurality of piezoelectric plates. For example, the laminated piezoelectric actuator expands by several to several tens of microns upon applying a voltage to the piezoelectric plates, and works as a source of driving the actuator.
The above laminated piezoelectric actuator is constituted by a pole-like laminate in which piezoelectric layers and internal electrode layers are alternately laminated one upon the other, and external electrode plates provided on the opposing side surfaces of the pole-like laminate and are electrically connected to the internal electrode layers. The internal electrode layers are alternately exposed at their ends on both side surfaces of the pole-like laminate, and the alternately exposed ends are electrically connected to the external electrode plates on the side surfaces thereof. Namely, on each of the side surfaces, every other internal electrode layers are connected to the external electrode plate, and the internal electrodes neighboring up and down are connected to the different external electrode plates so as to be applied with voltages of polarities different from each other.
In producing the above laminated piezoelectric actuator, so far, a paste for internal electrodes is applied onto a ceramic green sheet that serves as a piezoelectric layer, a plurality of green sheets on which the paste is applied are laminated to prepare a laminated molded article which is, then, fired to prepare a pole-like laminate, and the side surfaces of the pole-like laminate are polished to precisely finish the shape of the product (see prior art (A): Japanese Unexamined Patent Publication (Kokai) No. 2003-17779).